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Histology > Endocrine Glands > Flashcards

Endocrine Glands Flashcards

1
Q

what is the endocrine system?

1. what is it composed of?

A
  1. the endocrine system is composed of several ductless glands, clusters of cells within certain organs, and isolated endocrine cells, diffuse neuroendocrine system (DNES) cells, in the epithelial lining of the gastrointestinal and respiratory systems
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2
Q

what are the glands of the endocrine system called?

A

the glands of the endocrine system include:

    - pituitary gland
    - thyrois gland
    - parathyroid gland
    - adrenal gland
    - pineal gland
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3
Q

what is the function of the endocrine system?

A

function of endocrine glands is to secrete hormones into nearby capillaries, which interact with the nervous system to modulate and control the bodys metabolic activites

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4
Q

what are hormones?

A

hormones are chemical messengers that are carried via the bloodstream to distant target cells.
hormones include low-molecular weight water-soluble proteins and polypeptides and lipid-soluble substances, principally the steroid hormones

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5
Q

what are water-soluble hormones?

1. what do they interact with (two types of receptors)

A

water soluble hormones are proteins and polypeptides, which include:
- insulin, glucogon, FSH

  1. water-soluble hormones interact with specific cell surface receptors on target cells, whcih communicate a message that generates a biological response by the cell.
    • G protein-linked receptors leads to second messenger that evokes a target cell response
    • catalytic receptors are used by insulin and GH.
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6
Q

what are lipid-soluble hormones?

A

lipid-soluble hormones diffuse across the plasma membrane of target cells and bind to specific receptors on the cytosol or nucleus, forming hormone-receptor complexes that regulate transcription of DNA

  • principally steroid hormones!
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7
Q

where is the hypophysis located?
what two divisions is the pituitary (hypophysis) gland split into?
where are they derived from?

A

the pituitary gland lies below the hypothalmus, to which it is connected.

the pituitary is divided into:

 - the anterior (adrenophysis) 
 - the posterior (neurophysis)

each subdivision is dervied from a distinct embryonic analog.

- anterior: ectodermal diverticulum of the stomoderm
- posterior: hypothalmus
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8
Q

how is the adenohypophysis subdivided?

A

the adenohypophysis is subdivided into:

- the pars distalis
- the pars intermedia 
- the pars tuberalis
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9
Q

what is the structure of the pars distalis?

  • capsule
  • cells
A

the pars distalis is supported by a connective tissue capsule and framework.
the pars distalis consists of regular cords of parenchymal cells lying next to fenestrated capillaries

the parenchymal cells include:

- chromophils
- chromophobes
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10
Q

what are chromophils located in the adenohypophysis?

  1. how are they regulated?
  2. how are they classified (two types)?
A

chromophils are parenchymal cells that stain intensely because of their hormone-containing secretory granules found in the pars distalis.

chromophils synthesise, store and release several hormones.

  1. chromophils are regulated by specific stimulatory and inhibitory hormones produced by neurosecretory cells in the hypothalmus and are conveyed to the pars distalis via a system of portal blood vessels originating in the median eminence.
  2. chromophils are classified into two types depending on the dyes they bind to:
    - acidophils (acid dyes, stain orange/red)
    - basophils (basic dyes, stain blue)
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11
Q

what are the acidophils of the adenohypophysis?

what are the two subtypes of acidophils?

A

acidophils are a class of chromophils found in the pars distalis. they are small cells of two subtypes:

 1. somatotrpohs
 2. mammotrophs
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12
Q

what are somatotrophs?
what do they produce?
how are they stimulated?
how are they inhibited?

A

somatotrophs are a subtype of acidophils, which is a class of chromophils found in the adenohypophysis.

somatotrophs produce somatotropin (growth hormone)
somatotrophs are stimulated by SRH
somatotrophs are inhibited by somatostatin

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13
Q

what are mammotrophs?
what do they produce?
how are they stimulated?
how are they inhibited?

A

mammotrophs are a subtype of acidophils, which are a class of chromophil found int he adenohypophysis.

mammotrophs produce prolactin stored in small secretory granules
mammotrophs stimulated by PRH
mammotrophs inhibited by PIH

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14
Q

what are the basophils of the adenohypophysis?

what are the three subtypes of basophils?

A

basophils are a class of chronophils found in the pars distalis. basophils are of three subtypes:

1. corticotrophs
2. thyrotrophs
3. gonadotrophs
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15
Q

what are corticotrophs?
what do they produce?
how are they stimulated?

A

corticotrophs are a subtype of basophils, which is a class of chromophil found in the par distalis of the adenohypophysis.

corticotrophs produce adenocorticotropic hormone (ACTH) and lipotropic hormone (LPH)

corticotrophs stimulated by corticotropin-releasing hormone (CRH)

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16
Q

what are thyrotrophs?
what do they produce?
how are they stimulated?

A

thyrotrophs are a subtype of basophils, which is a class of chromophil found in the par distalis of the adenohypophysis.

thyrothrophs produce TSH
thyrothrophs are stimulated by thyrotropin-releasing hormone (TRH)

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17
Q

what are gonadotrophs?
what do they produce?
how are they stimulated?

A

gonadotrophs are a subtype of basophil, which is a class of chromophil found in the adenohypophyis.

gonadotrophs produce FSH and LH in both sexes. in males LH is reffered to as interstitial cell stimulating hormone (ICSH)

gonadotrophs are stimulated by gonadotropin releasing hormone (GnRH) also known as LHRH

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18
Q

what are chromophobes located in the adenohypophysis?

A 
chromophobes are a class of parenchymal cells that stain poorly. 
they are small cells that lack secretory granules arranged in clusters close to other clusters.

they are suggested to be acidophils and basophils in various stages of their life cycles.

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19
Q

what are folliculostellate cells located in the adenohypophysis?

A

folliculostellate cells are numerous in the pars distalis and lie between the chromophils and chromophobes.

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20
Q

what is the pars intermedia?

  • location
  • structure
  • what do they secrete?
A

the pars intermedia is a subdividion of the adenohypophysis that lies between the pars distalis and the pars nervosa (of the neurohypophysis)

the pars intermedia contains many colloid-containing cysts (rathke cysts) that are lined by cuboidal cells

it also possesses basophilic cells that secrete promelanocortin (POMC), which is cleaved to melanocyte-stimulating hormine (MSH)

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21
Q

what is the pars tuberalis?

  • location
  • structure
A

the pars tuberalis is a subdivision of the adenohypophysis that surrounds the cranial part f the infundibulum (hypophyseal stalk)

the pars tuberalis is composed of cuboidal basophilic cells, arranged in cords along an abundant capillary network

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22
Q

how is the neurohypophysis subdivided?

A

the neurohypophysis (posterior pituitary) is subdivided into the pars nervosa and the infundibulum

  • pars nervosa is the main body
  • infundibulum is continuous with the hypothalmus
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23
Q

what is the hypothalamohypophyseal tract?

what does it transport?

A

the hypothalamohypophyseal tract contains unmyelinated axons of the neurosecretory cells whose bodies are located int he supraoptic and paraventricular nuclei of the hypothalmus.

the tract transports oxytocin, antidiuretic hormone (ADH, vasopressin), neurophysin and ATP to the pars nervosa

24
Q

what are the nuclei in the hypothalumus called that produce hormones to transport to the pars nervosa of the neurohypophysis?
what hormones do they produce?

A

supraoptic nucleus
paraventricular nucleus

they produce oxytocin and ADH

25
Q

what is the main function of oxytocin
where is it produced?
where is it stored?

A

oxytocin is an hormone that induces contraction of smooth muscle in the wall of the uterus at parturition.

oxytocin is produced in neurosecretory cells of the hypothalmus (supraoptic and paraventricular nuclei)

oxytocin is stored in Herring boddies, distal ends of the hypothalamohypophyseal axons.

26
Q

what is the main function of vasopressin
where is it produced?
where is it stored?

A

Vasopressin or ADH is a hormone that renders the kidney collecting tubules permeable to water, which is resorbed to produce a concentrated urine
It also constricts the smooth muscle in wall of arterioles

ADH is produced in neurosecretory cells of the supraoptic and paraventicular nuclei found in the hypothalmus.

it is then transported through hypothalamohypophyseal axons and stored at the distal ends in accumulations known as Herring bodies.

27
Q

what is the pars nervosa?

what does the pars nervosa release?

A

the pars nervosa is a division of the neurohypophysis. it contains distal ends of the hypothalamohypophyseal axons and is the site where the neurosecretory granules in these axons are stored ready for their release (Herring bodies)

the pars nervosa releases oxytocin and ADH into fenestrated capillaries in response to nerve stimulation.

the pars nervosa also contains pituicytes

28
Q

what are pituicytes?

  • location
  • function
A

pituicytes occupy 25% of the volume of the pars nervosa of the neurohypophysis.

they are glial-like cells that support the axons in the region

their cytoplasmic processes are numerous and contain lipid droplets, intermediate filaments and pigments.

29
Q

vasculariation of the pituitary gland: describe the arterial supply of the pituitary gland…

A

the arterial supply is from two pairs of blood vessels derived from the internal carotid artery.
1. the right and left superior hypophyseal arteries serve the pars tuberalis, infundibulum and the median eminence

 2. the right and left inferior hypophyseal arteries searve mostly the pars nervosa
30
Q

vasculariation of the pituitary gland: what is the primary capillary plexus?

  • location
  • drainage
A

the primary capillary plexus is apart of the hypophyseal portal system and consists of fenestrated capillaries coming off the superior hypophyseal arteries.

 1. this plexus is located in the median eminence, where stored hypothalamic neurosecretory hormones enter the blood
 2. it is drained by the hypophyseal portal veins, which descend through the infundibulum into the adenohypophysis.
31
Q

vasculariation of the pituitary gland: what is the secondary capillary plexus?
- location

A

the secondary hypophyseal plexus is a part of the hypophyseal portal system consisting of fenestrated capillaries coming off the hypophyseal portal vein.
1. located in the par distalis where neurosecretory hormones leave the blood to stimulate or inhibit the parenchymal cells.

32
Q

how is the pars distalis of the adenohypophysis regulated?

A
  1. neurosecretory cells in the hypothalmus synthesise specific hormones that enter the hypophyseal portal system and stimulate or inhibit the parenchymal cells of the pars distalis
  2. the hypothalamic neurosecretory cells in turn are regulated but he level of hormones in the blood (negative feedback) or by other phyiological factors
  3. some hormones exert negative feedback on the par distalis directly.
33
Q

what is the structure of the thymus gland?

  • gross
  • capsule (other glands?)
  • subdivision
A

the thyroid gland is composed of two lobes connected by an isthmus.
the thyroid is surrounded by a dense irregular collagenous connective tissue capsule, which the parathyroid glands are embedded

the thyroid gland is subdivided by capsular septa into lobules containing follicles. these septa also serve as conduits for blood vessels, lymphatic vessels and nerves.

the thymus contains thyroid follicles which contain follicular cells and parafollicular cells.

34
Q

in the thyroid gland, what are thyroid follicles?

structure and function

A

thyroid follicles are spherical structures filled with colloid.
colloid is a viscous gel consisting mostly of iodinated thyroglobulin.

  1. structure: a single layer of follicular cells (epithelial cells) surround the colloid within each follicle. one or more parafollicular cells lie sandwiched between the follicular cells.
    both of these parenchymal cell types rest upon the basal lamina surrounding the follicle, whcih separates them from the abundant network of fenestrated capillaries in the connective tissue.
  2. function: thyroid follicles synthesise, store and release thyroid hormones
35
Q

in the thyroid gland, what is the structure of follicular cells?

A

follicular cells surround the thyroid follicles. they are cuboidal epithelial cells that become columnar when stimulated and squamous when inactive.

follicular cells possess a distended RER with many ribosome-free regions, a supranuclear golgi complex, many lysosomes and rod-shaped mitochondria

follicular cells also contain many small aplical vesicles, which are involved in the transport and release of thyrogobulin and enzymes into the colloid

follicular cells also posses short, blunt microvilli that extend into the colloid

36
Q

in the thyroid gland, what is the function of follicular cells?

A

follicular cells synthesise and release the thyroid hormones, thyroxine (T4) and triiodothyronine (T3) occur by a sequence of events.

these processes are evoked by thyroid stimulating hormone (TSH) which binds to G protein-linked receptors on the basal surface of follicular cells

37
Q

in the thyroid gland, what are parafollicular glands?

  • structure
  • function
A

parafollicular cells are present singly or in small clusters of cells between the follicular cells and basal lamina. these cells are DNES cells or enteroendocrine cells.
they possess elongated mitochondria, substantial amounts of RER, a well-developed golgi complex and many membrane bound dense secretory granules

the function of parafollicular cells is to sythesise and release calcitonin, a peptide hormone, in response to high blood calcium levels.

38
Q

what is calcitonin?

  1. where is it produced and released?
  2. what is its function?
A

calcitonin is a peptide hormone

  1. it is synthesised and released by parafollicular cells in the thyroid gland
  2. calcitonin functions primarily to lower blood calcium levels by inhibiting bone resorption by osteoclasts.
39
Q

what are T3 and T4?

A

T3 and T4 are thyroid hormones produced in the follicular cells of the thyroid gland. they act on a variety of target cells to increase the basal metabolic rate and thus promote heat production
they have broad effects on gene expression and the induction of protein synthesis

40
Q

what is the parathyroid gland?

  • location
  • structure
A

the parathyroid glands are four small glands found on the posterior surface of the thyriod gland, invested the thyroid connective tissue capsule.

the parathyroid contains parenchyma composed of twp types of cells, supported by septa from the capsule , whcih penetrate each gland and convey blood vessels into its interior.

41
Q

what are the two types of parenchymal cells found in the parathyroid gland?

A

the two types of parenchymal cells found in the parathyroid gland are:

1. oxyphil cells
2. cheif cells
42
Q

what happens to the parathyroid gland in older persons?

A

the parathyroid becomes infiltrated with fat cells and the number of oxyphil cells increases.

43
Q

in the parathyroid gland, what are cheif cells?

  • structure
  • function
A

cheif cells are small basophilic cells arranged in clusters
cheif cells form anastomosing cords, surrounded by a rich, fenestrated capillary network
cheif cell posses a central nucleus, a well-developed golgi complex, abundant RER, small mitochindria, glycogen and secretory granules of variable size.

cheif cell functions to synthesise and secrete parathyroid hormone (PTH) which raises blood calcium levels. high blood calcium levels inhibit the production of PTH

44
Q

in the parathyroid, what are oxyphil cells?

A

oxyphil cells are large, eosinophilic cells that are present singly or in small clusters within the parenchyma of the gland

oxyphil cells possess many large, elongated mitochondria, poorly developed golgi complex and limited amount of RER

oxyphil cells have an unknown function

45
Q

what is PTH?
where is it synthesised and secreted?
what is its function?

A

PTH (parathyroid hormone) is synthesised and secreted by cheif cells of the parathyroid gland.

PTH increases the blood calcium level by indirectly stimulating osteoclasts to resorb bone

46
Q

where are the adrenal glands found?

A

the adrenal glands are found on the superior pole of each kidney

47
Q

where are the adrenal glands derived?

A

the adrenal glands are derived from two embryonic sources:

- ectodermal neural crest (adrenal medulla)
- mesoderm (adrenal cortex)
48
Q

how are the adrenal glands divided?

A

the adrenal glands are divided into two regions based their embryonic sources.

- the adrenal cortex
- the adrenal medulla
49
Q

what is the structure of the adrenal cortex of the adrenal glands?

A

the adrenal gland is covered by their own collagenous capsule
the adrenal cortex contain parenchymal ells that synthesise and secrete but DO NOT store various steroid hormones

the adrenal cortex lies beneath the capsule and is divided into 3 concentric histologically distinct zones.

1. zona glomerulosa
2. zona fasciculata
3. zona reticularis
50
Q

what is the structure and function of the zona glomerulosa of the adrenal cortex of the adrenal glands?

A

the zona glomerulosa is the outer concentric layer of the adrenal cortex.

the zona glomerulosa is composed of small cells arranged in arch-like cords and clusters. these cells have a few small lipid droplets, an extensive SER and mitochindria with shelflike cristae

zona glomerulosa synthesises and secretes mineralocorticoids (mostly aldosterone)
the hormone production is stimulated by angiotensin II and ACTH (adrenocorticotropic hormone)

mineralocorticoids regulate electrolye, water balance via effect on cells of renal tubules

51
Q

what is the structure and function of the zona fasciculata of the adrenal cortex of the adrenal glands?

A

the zona fasciculata is the middle region of the adrenal cortex of the adrenal glands.

the zona fasciculata is composed of columns of cells and sinusoidal capillaries orientated perpendiculary to the capsule. these cells contain many lipid droplets.

the zona fasciculata synthesise and secretes glucocorticoids (cortisol and corticosterone).
hormone production is stimulated by ACTH

52
Q

what is the structure and function of the zona reticularis of the adrenal cortex of the adrenal glands?

A

the zona reticularis is the inner zone of the adrenal cortex.
the zona reticularis is composed of cells, arranged in anatomosing cords.
the cells synthesises and secretes weak androgens.
hormone production is stimulated by ACTH

53
Q

what hormone stimulates the production of hormones of the adrenal cortex?

A

ACTH - adrenocorticotropic hormone

54
Q

what is the adrenal medulla of the adrenal glands?

A

the adrenal medulla is completely invested by the adrenal cortex contains two populations of parenchymal cells, called chromaffin cells, which synthesise, store and secrete the catecholamines epinephrine and norepinephrine.

55
Q

what are chromaffin cells?
where are they found?
what do they release?

A

chromaffin cells are parenchymal cells found in the adrenal cortex of the adrenal glands.
chromaffin cells are large, polyhedral cells containing secretory granules that stain intensely with chromium salts.
chromaffin cells are arranged in short, irregular cords surrounded by extensive capillary network.
they possess well-developed golgi complex, isolated regions of RER and numerous mitochondria.

they produce, store and secrete epinephrine and norepinephrine.

56
Q

how is blood supplied to the adrenal glands?

A

blood supplied to the adrenal gland is derived from the superior, middle and inferior adrenal arteries, which form three groups of vessels: to the capsule, to th eparenchymal cells of the cortex and directly to the medulla.

Histology (16 decks)

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